Evidence Based Sleep Tips To Support Metabolism

Sleep And Blood Sugar Control

When sleep is compromised (even if it's just one night), it appears to make your cells less sensitive to insulin. 

Insulin is a hormone that helps move blood sugar (glucose) out of the bloodstream and into cells where the body can use it. When cells don't respond to insulin or become resistant to it, glucose levels remain elevated in the blood longer than they should, and damage starts to happen. 

So let's say you always eat an apple in the morning. After a bad night's sleep, that same apple could spike your blood sugar, whereas after sleeping well, you'd have a much more even rise and fall in glucose levels.

Over time, this impaired blood sugar control may lead to consistently elevated blood glucose, a risk factor for pre-diabetes. One study found that the odds of prediabetes among over 2,000 healthy adults doubled for those who reported sleeping five or fewer hours a night compared to those who slept around seven hours a night.

Short sleep duration is also a risk factor for diabetes. Another study that pooled data from over one million individuals found that those sleeping five or fewer hours were 48% more likely to develop diabetes. This is why I highlight sleep as one of the 5 key strategies in my guide on how to lower HbA1c naturally.

Poor Sleep Increases Appetite

Not sleeping well directly messes with your hunger hormones. The hunger hormone (ghrelin) is ramped up, and the hormone that signals to the brain that you're full (leptin) decreases.

This can increase appetite and cravings, making maintaining a healthy weight more challenging. Studies show that people who sleep less snack more and opt for more high-calorie foods. They also eat less protein and fibre, two nutrients that are essential for overall health and for helping us manage our weight).

So, sufficient sleep is needed to help us make that healthful choice when we are presented with the decision of a salad or a slice of cake at lunchtime.

Poor Sleep Can Stress Your Body Out 

Not only can sleeping poorly stress you out, but stress can make it challenging to fall asleep and stay asleep. It's a vicious cycle that's disruptive to your health. 

Cortisol is known as our stress hormone, and it's not always a bad thing. We do need some of this in our everyday lives. Cortisol levels naturally peak in the morning (to help get you out of bed) and drop to their lowest levels at night (right as melatonin levels increase to induce sleepiness). 

However, chronically elevated cortisol levels are not good; they can increase appetite and are linked to increased fat storage around the middle, known by many as "belly fat." Interestingly, oestrogen can help balance cortisol levels, and this is why, around menopause, when women's oestrogen levels start to drop, they start to complain of middle-aged spread, particularly around the tummy.

Research shows that sleep deprivation leads to higher daytime cortisol levels.

Poor Sleep & Body Composition

By body composition, I mean the ratio of muscle to body fat in your body, not just the number on the scale.

High insulin paired with high cortisol from sleep loss is a recipe for  negative changes to body composition,

As these hormones tell the body to hold on to fat, soft tissues (like muscles) become a more appealing energy source. So fat mass increases, and lean muscle mass decreases, which slows your metabolism long term. 

Poor Sleep Lowers Your Energy To Exercise

This is a pretty obvious one.. if you're not sleeping, the last thing you will want to do is exercise.

Exercise benefits metabolic health in many ways. It helps with blood sugar control and insulin sensitivity, increases daily energy expenditure, builds lean muscle mass, improves blood pressure, and more. 

But if you're tired, exerting yourself physically may not sound appealing. Research shows that fatigued adults not only get less moderate to vigorous exercise, but they also take fewer steps and engage in more sedentary behaviours (like napping, lounging, or resting). 

And as exercise can actually help you sleep, this can be a bit of a vicious cycle.

Evidence-Based Sleep Tips

• Research has shown that eating two kiwis one hour before bed can improve sleep onset, duration, and efficiency. Tart cherry juice also has similar benefits. This is why they are both included in my bedtime snacks for weight loss post.

• Having a regular eating pattern with set meal times helps feed into our internal clock so your body knows what time of day it is. This in turn helps with sleep patterns. Try to eat breakfast around the same time each day, and the same with lunch and dinner.

• Aim to keep caffeine intake moderate (around 200 mg or less per day) and try to avoid it after lunch. Even if you feel like coffee doesn’t affect how quickly you fall asleep, research shows it can still reduce the amount of deep sleep you get, which is the most restorative stage of sleep. Caffeine isn’t just in coffee, it’s also found in dark chocolate, energy drinks, and some teas. It’s a stimulant with a half-life of about 6 hours, meaning half of the caffeine you consume is still in your system 6 hours later, a quarter remains after 12 hours, and small amounts can linger well into the night.

• The optimal time for your last big meal is at least three hours before bed. However, you don't want to go to bed hungry, so for some, a small bedtime snack is necessary.

• Have a bedtime alarm. 95% of my clients are very good at telling me what time they wake up in the morning. For example, "My alarm goes off at 6.15 am every Mon-Fri,". But when I ask what time they're going to bed, only about 5% can give me a proper answer. Set an alarm and have an official wind down routine start time. This lets your body know when you're preparing for sleep with subtle cues.

How Light Impacts Sleep

Light plays a key role in regulating our body clock and melatonin, the hormone that helps us fall asleep. Our brains naturally release melatonin in response to darkness, but exposure to bright light in the evening can suppress its production and make it harder to drift into deep, restorative sleep.

Because modern life keeps us surrounded by artificial light, dimming the lights around your home in the lead-up to bedtime can help signal to your body that it’s time to wind down. Aim to keep your bedroom as dark as possible, and consider blackout curtains or a sleep mask, as light can continue to disrupt sleep quality even after you’ve fallen asleep.

Blue light from phones, TVs, tablets, and computers is especially disruptive to melatonin release. For this reason, it’s best to limit screen use in the two hours before bed where possible. I often encourage having a “bedtime” for your phone before your own, but if you do need to use electronics, switching on night-mode settings (like Night Shift on iPhones) or using blue light-blocking glasses can help reduce the impact.

Morning light is just as important for sleep regulation, so try to get outside before midday if you can, even for a short walk. Natural light helps lower melatonin levels earlier in the day, making you feel more alert, and helps your body build a stronger contrast between daytime and nighttime, which supports better sleep later on.

Exercise And Sleep

Daily exercise promotes better sleep. Try and keep your body moving, especially in the morning. Considering the benefit of morning light, consider exercising outdoors.

Best Temperature For Improved Sleep

We don’t sleep as well when we’re too warm, so in addition to aiming for a dark room, it’s also helpful to keep your bedroom cool. For most people, about 15–19 °C (60–67 °F) supports more restful sleep, and ideally your bedroom should be the coolest room in the house. Interestingly, a warm shower or bath before bed can actually help. It raises skin temperature and triggers a subsequent drop in core body temperature, which sends a signal to your brain that it’s time to sleep.

Brain Dump Before Bed

Another thing many of my clients find really helpful for sleep is doing a quick “brain dump” before bed.

This just means grabbing a pen and paper and writing down anything that’s running through your head, to-do lists, worries, random thoughts, all of it. It’s especially useful if you tend to overthink at night.

I always suggest keeping the notebook beside your bed too, so if a thought pops into your head while you’re trying to fall asleep, you can jot it down and let your brain relax again instead of spiraling on it.

Sleep Stories For Better Sleep

Sleep stories can also be really effective, especially if you struggle to switch your mind off at night. I personally like using the app Insight Timer, which has a whole section of free sleep stories that are great for relaxing and drifting off.

Some people also find counting backwards helpful, or listening to an audiobook, just maybe not an intense thriller that keeps you on edge!

Ideally though, you want to avoid scrolling on your phone or using laptops and tablets before bed, as the light and stimulation can make it harder for your brain to fully switch off.

Melatonin Supplements And Sleep

There is evidence that oral melatonin can help people fall asleep faster and slightly improve overall sleep quality, particularly for those struggling with disrupted sleep schedules, stress, or jet lag.

However, it’s important to remember that light exposure is still the strongest regulator of your body’s natural melatonin production. Bright lights in the evening (especially from phones, tablets, and laptops) can significantly reduce melatonin release, even if you take a supplement.

The reassuring news is that short-term melatonin use, in studies lasting from around one week to one month, does not appear to suppress your body’s own melatonin production in healthy adults.

That said, research has shown that many melatonin supplements don’t contain the amount listed on the label. Some contain far less than stated (which may make them ineffective), while others contain much more (which can increase the risk of side effects like grogginess or vivid dreams). This is why choosing a trusted, third-party tested supplement is important.

My approach with clients is always to focus on sleep habits first, things like light exposure, routines, stress management, and caffeine timing. If sleep is still a struggle after that, a short trial of melatonin may be worth considering.

Melatonin is not authorized for over-the-counter (OTC) sale in the United Kingdom, most of the European Union, and Japan. In these places, it is classified as a prescription-only medicine.

If you do choose to take a melatonin supplement, I recommend a low dose of 1-3mg and try to avoid taking it for long periods of time. I like the Nordic Naturals Zero Sugar Melatonin gummies. These are third party tested and provide 1.5mg per gummy.

Magnesium Supplements And Sleep

Magnesium plays an important role in sleep, and higher magnesium intake from food has been linked with better sleep quality The good news is that magnesium-rich foods are easy to include in most diets, so aiming to meet your daily needs through food should always be the first step.

In certain groups, such as older adults or people who train heavily and lose more minerals through sweat, magnesium supplements have been shown to improve sleep quality.

If someone does choose to supplement, a commonly used option is magnesium glycinate taken about 30–60 minutes before bed (around 200–300 mg).

It’s important not to overdo supplements, as too much supplemental magnesium can cause digestive upset, which is why the upper limit for magnesium from supplements is set at 350 mg per day. Forms like magnesium oxide are also more likely to cause stomach issues and are less well absorbed.

Bottom Line

Do not neglect your sleep. You can try all the meal plans and diets in the world, but if you're not getting adequate sleep, you will be fighting an uphill battle in terms of health and managing your weight.

If you have any questions, feel free to comment below, I'm always happy to help.